# Homework Help: EGR ratio from exhaust gas composition

1. Jul 31, 2017

### mrcarbon4hydrohen

1. The problem statement, all variables and given/known data
given:-fuel and air mass flow, measured mole ratios of exhaust composition y_i. Lets assume stoichiometric combustion so we have only CO2, H20 and N2 as products.

2. Relevant equations
Can EGR ratio be calculated from available data?

3. The attempt at a solution

I get result that molar ratios don't depend on EGR ratio.

2. Jul 31, 2017

### Staff: Mentor

3. Aug 24, 2017

### mrcarbon4hydrohen

I have another question. I there is excess air, can EGR be determined? Folowing the same logic as before, it can't. This time I used a slightly different formula but result is the same.

but..
I found a SAE paper in which (Fresh Air+EGR)/Fuel ratio is determined by exhaust concentrations. So I think there is connection between EGR and gas concentations in exhaust. This is the paper(you can see in preview of SAE paper what I am reffering to, equation (3)): http://papers.sae.org/2010-01-1285/ .I tried to get solution as in paper, but got different result.

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4. Aug 26, 2017

### Staff: Mentor

As best I can tell, the mole fractions of the gases in the exhaust are independent of the recycle ratio.